Field of the Invention
The present invention relates to an image forming device, an image forming method and a program, and in particular to an image forming device, an image forming method and a program which digitally correct a curve component of a laser beam and a mechanical inclination component.
Description of the Related Art
For correcting a color shift between colors in a color image forming device of a so-called tandem type, as shown in Japanese Patent No. 2633877, there is a method where a pattern image for registration correction is formed on an intermediate transfer belt and the pattern image is read with an image sensor. In such a method, a shift amount between pattern images for registration correction of the respective colors obtained by the reading is feedback-controlled to the image forming process of color plate image of each color (C, M, Y, K) to correct the color shift of each color.
On the other hand, there is known a method in which, for example, by an application of a technology disclosed in Japanese Patent No. 3388193, costs are reduced by cutting down on the process of a laser scanner adjustment and digitally correcting a curve component of a laser beam in an electronic photography-related image forming device.
For example, in the digital correction in a sub scan direction of a scan line, an image is formed by appropriately changing a line of the image data to be formed to be capable of canceling out a curve amount based upon a curve component of the laser beam beforehand obtained. That is, when the laser beam is shifted by one line lower for a sub direction of the laser on certain position of a main scan direction of the laser, in order to correct the shift, image data of one line upper on certain position of the sub direction of the laser is read from a memory which stores the image data. And the image of the image data is formed. Here, a line is a collection of pixels arranged in the main scan direction.
In detail, for example, when a curve component of a laser beam is expressed by f(x) to a main scan position X, numeral-y obtained by rounding off f(x) is set as a line changing amount and all of data of a section from xi to xj which the line changing amount is equal are shifted by a −y line amount. When this is applied to all image regions, the curve component of the laser beam can be cancelled out to reproduce an original image.
Further, as another technology, there is a method in which the above color shift correction of the respective colors and the digital correction processing are combined to digitally correct a mechanical inclination component together with the curve component of the laser beam.
In this case, an allowance amount of the color shift correction of each color is frequently very similar to a line changing amount by the mechanical inclination component. In a case of forming a pattern image for registration correction without consideration of the mechanical inclination component, the formed pattern image possibly exceeds a range in which a device can measure the formed pattern image as the color shift amount. In such a case, the color shift can not be corrected.
In such a case, the correction may be possible by variously modifying the color shift amount measurement and the calculation processing for correction, but the processing itself can be complicated or a plurality of the exceptional processing become required. For avoiding this event, it is preferable that the pattern image for the registration correction is also formed on the intermediate transfer belt by performing digital correction including the above line changing processing in consideration of the curve component of the laser beam and the mechanical inclination component.
However, in a case of performing the digital correction to the mechanical inclination component in addition to the curve component of the laser beam as in the case of the conventional technology, the curve component of the laser beam is always constant and on the other hand, the mechanical inclination component is a variable data. The curve component of the laser beam is a fixed data because of dependence on a mounting position of a laser scanner unit to a color image forming device.
Therefore, in regard to formation of the pattern image for the registration correction at the time of performing the color shift amount measurement, the following processing is required to be executed. That is, an update mechanical inclination component is always applied to the pattern image for the registration correction to generate an image and the color shift amount measurement is required to be performed using the pattern image for the registration correction including the correction of the mechanical inclination component.
If it is required simply to correct only a fixed value such as the curve component of the laser beam without consideration of the mechanical inclination component in regard to formation of the pattern image for the registration correction upon performing the color shift amount measurement, the following processing may be executed. That is, the pattern image for the registration correction which is corrected by the predetermined curve component of the laser beam is stored in advance and this pattern image is formed as an image by the laser. And the color shift amount measurement may be performed by this image formed by the pattern image. In this case, the pattern image for the registration correction may use a fixed image to which the line changing processing to cancel out the curve component of the laser beam in advance known is executed.
However, the following processing is required to be executed for regularly applying the update mechanical inclination component for the pattern image for the registration correction at each time of measuring the color shift amount. That is, it is required to update the pattern image for the registration correction at each time of measuring the color shift amount based on the measured color shift without setting the pattern image for the registration correction as the fixed image data.
On the other hand, in the recent image forming device, there is known a printing processing system in which all the processing in regard to the image generation is executed in a local PC side for reducing hardware costs.
Since in such an image forming device, the image generation is performed on the local PC, there is a problem that the image formation can not be made without the local PC.
In addition, in a case where in a system for performing an image generation on the local PC, the color shift amount measurement fails because of any cause to again generate a pattern image for registration correction, there occurs the following problem. That is, when the processing is executed on the local PC in consideration of the curve component of the laser beam and the mechanical inclination component, the error processing may be complicated.
In addition, even if the pattern image for the registration correction in which the color shift amount measurement has previously failed is used for once more performing the measurement, there is the problem with the possibility of the re-failure.
The present invention is made in view of the foregoing problem and an object of the present invention is to be capable of executing color shift correction processing in consideration of a mechanical inclination component even in a printing system to which a local PC is connected.
In addition, another object of the present invention is to provide a method of re-measurement in which, even in a case where any problem occurs on a printing device and the color shift correction processing fails, there are the high probability of no failure and no complication of the processing.